Gate-tunable unconventional superconductivity in 2D oxide interfaces nanodevices

In conventional Bardeen-Cooper-Schrieffer superconductors, inversion and time-reversal symmetries are preserved. The breaking of these symmetries is expected to lead to the formation of unconventional superconducting pairing. In this respect, the two-dimensional (2D) electron systems in SrTiO₃ based heterostructures, such as LaAlO₃/SrTiO₃, is a paradigmatic non-centrosymmetric superconductor due to the coexistence of gate tunable large Rashba spin-orbit coupling and ability to modulate multi-orbital 2D superconductivity.  We present experimental evidence of unconventional superconductivity in the LaAlO₃/SrTiO₃ interface nano-devices. The central observations are the giant anomalous enhancement of the critical current by small out-of-plane magnetic fields and the asymmetric response with respect to the magnetic field direction. These features have a unique trend in intensity and sign upon electrostatic gating that, together with their dependence on temperature and nanowire dimensions, cannot be accommodated within a scenario of spin-singlet superconductivity. We theoretically demonstrate that the hallmarks of the experimental observations unambiguously indicate the coexistence of Josephson channels with intrinsic phase shifts due to different sign of the order parameter.